High frequency helical amplifier and oscillator

Abstract

Disclosed herein is a class of mm and sub mm wavelength amplifiers and oscillators operating with miniature helical slow wave circuits manufactured using micro fabrication technology. The helices are supported by diamond dielectric support rods. Diamond is the best possible thermal conductor, and it can be bonded to the helix. The electron beam is transmitted, not through the center of the helix, but around the outside. In some configurations the RF power produced may be radiated directly from the slow wave circuit. The method of fabrication, which is applicable above 60 GHz, is compatible with mass production.

1. A slow wave circuit of an electron device, the slow wave circuit comprising:
 a helical conductive structure, wherein an electron beam flows around the outside of the helical conductive structure and is shaped into an array of beamlets arranged in a circular pattern surrounding the helical conductive structure; 
 a generally hollow barrel containing the helical conductive structure; and 
 a pair of dielectric support structures attached to the helical conductive structure and the hollow barrel. 
 
     
     
       2. The slow wave circuit of  claim 1 , wherein the electron device comprises a traveling wave tube (TWT). 
     
     
       3. The slow wave circuit of  claim 2 , wherein a spent beam emerging from the TWT is captured in a multistage depressed collector. 
     
     
       4. The slow wave circuit of  claim 1 , wherein the electron device comprises a backward wave oscillator (BWO). 
     
     
       5. The slow wave circuit of  claim 4 , wherein a spent beam emerging from the BWO is captured at low energy in a two stage collector that traps the electrons between crossed magnetic and electrical fields. 
     
     
       6. The slow wave circuit of  claim 1 , wherein the hollow barrel includes four equally spaced slots placed symmetrically about the pair of dielectric support structures. 
     
     
       7. The slow wave circuit of  claim 1 , wherein the dielectric support structures are comprised of diamond. 
     
     
       8. The slow wave circuit of  claim 1 , wherein the hollow barrel is comprised of diamond. 
     
     
       9. The slow wave circuit of  claim 1 , wherein the circuit operates at a frequency greater than 60 GHz. 
     
     
       10. The slow wave circuit of  claim 1 , wherein said helical conductive structure is integral with said support structures. 
     
     
       11. The slow wave circuit of  claim 10 , wherein said helical conductive structure is supported at every turn thereof. 
     
     
       12. The slow wave circuit of  claim 10 , wherein said helical conductive structure is supported on diametrically opposite sides by substantially co-planar supports. 
     
     
       13. The slow wave circuit of  claim 12 , wherein said supports include resonant loss patterns on at least one surface thereof. 
     
     
       14. The slow wave circuit of  claim 10 , wherein said support structures are studs. 
     
     
       15. The slow wave circuit of  claim 1 , wherein the pitch of said helical conductive structure is variable over the length thereof. 
     
     
       16. The slow wave circuit of  claim 15 , wherein said pitch is tapered for beam synchronism. 
     
     
       17. The slow wave circuit of  claim 12 , wherein said supports are dielectric. 
     
     
       18. The slow wave circuit of  claim 12 , wherein said supports are diamond. 
     
     
       19. The slow wave circuit of  claim 1 , wherein said helical conductive structure comprises two one-half helices bonded together. 
     
     
       20. The slow wave circuit of  claim 1 , including means for selective mode suppression. 
     
     
       21. The slow wave circuit of  claim 1 , wherein the hollow barrel is cylindrical in shape. 
     
     
       22. The slow wave circuit of  claim 2 , wherein the number of the beamlets is a function of the size of the helical conductive structure. 
     
     
       23. The slow wave circuit of  claim 2 , wherein number of the beamlets is a function of the current requirements of the slow wave circuit. 
     
     
       24. The slow wave circuit of  claim 2 , including a cathode; and
 wherein the array rotates about its axis less than about 5° per 4 mm axial travel to thereby avoid interference by the support structures for the helical conductive structure. 
 
     
     
       25. The slow wave circuit of  claim 2 , wherein the number of said beamlets is 6; and
 wherein the circumferential spacing of the beamlets is substantially equal. 
 
     
     
       26. The slow wave circuit of  claim 2 , including plural thermionic cathodes. 
     
     
       27. The slow wave circuit of  claim 2 , including plural field emitters. 
     
     
       28. The slow wave circuit of  claim 2 , including a single gridded cathode. 
     
     
       29. The slow wave circuit of  claim 9 , wherein said helical conductive structure is sized for operation at approximately 650 GHz. 
     
     
       30. The slow wave circuit of  claim 9 , where helical conductive structure is sized for operation over a bandwidth from about 60 GHz to about 1 THz. 
     
     
       31. The slow wave circuit of  claim 1 , where helical conductive structure is sized for operation at one of approximately 95 GHz and approximately 170 GHz. 
     
     
       32. The slow wave circuit of  claim 1 , wherein said helical conductive structure is microfabricated. 
     
     
       33. The slow wave circuit of  claim 32 , wherein fabrication of said helical conductive structure is by one of a group comprising lithography, reactive ion etching, deep reactive ion etching and selective metallization. 
     
     
       34. The slow wave circuit of  claim 32 , wherein the fabrication of said helical conductive structure is on a wafer scale compatible with mass production. 
     
     
       35. The slow wave circuit of  claim 1 , wherein said helical conductive structure is monofilar. 
     
     
       36. A slow wave circuit of an electron device having a cathode and a collector, the slow wave circuit comprising: a helical conductive structure between the cathode and the collector, wherein an electron beam flows around the outside of the helical conductive structure and is shaped into an array of beamlets arranged in a circular pattern surrounding the helical conductive structure; a generally hollow barrel containing the helical conductive structure, wherein the barrel is square in shape; and a pair of continuous dielectric support structures bonded to the helical conductive structure and the hollow barrel. 
     
     
       37. The slow wave circuit of  claim 36 , wherein the electron device comprises a traveling wave tube (TWT). 
     
     
       38. The slow wave circuit of  claim 37 , wherein a spent beam emerging from the TWT is captured in a multistage depressed collector. 
     
     
       39. The slow wave circuit of  claim 36 , wherein the electron device comprises a backward wave oscillator (BWO). 
     
     
       40. The slow wave circuit of  claim 39 , wherein a spent beam emerging from the BWO is captured at low energy in a two stage collector that traps the electrons between crossed magnetic and electrical fields. 
     
     
       41. The slow wave circuit of  claim 36 , wherein the continuous dielectric support structures are comprised of diamond. 
     
     
       42. The slow wave circuit of  claim 36 , wherein the hollow barrel is comprised of diamond. 
     
     
       43. The slow wave circuit of  claim 36 , wherein the circuit operates at a frequency greater than 60 GHz. 
     
     
       44. A slow wave circuit of a helical traveling wave tube wherein output power from the tube is launched directly into free space from a helical antenna that is an extension of a helix of the slow wave circuit. 
     
     
       45. The slow wave circuit of  claim 44 , wherein the output power is greater than about 270 mW. 
     
     
       46. The slow wave circuit of  claim 44 , wherein the output power thereof is greater than about 70 mW. 
     
     
       47. The combination of helical slow wave circuit and a helical antenna in which a helix of the slow wave circuit is directly connected to a helix of the antenna. 
     
     
       48. The combination of  claim 47  wherein said helical antenna is fabricated as an integral part of said helical slow wave circuit.